Diodes, and methods of forming diodes

ABSTRACT

Some embodiments include methods of forming diodes in which a first electrode is formed to have a pedestal extending upwardly from a base. At least one layer is deposited along an undulating topography that extends across the pedestal and base, and a second electrode is formed over the least one layer. The first electrode, at least one layer, and second electrode together form a structure that conducts current between the first and second electrodes when voltage of one polarity is applied to the structure, and that inhibits current flow between the first and second electrodes when voltage having a polarity opposite to said one polarity is applied to the structure. Some embodiments include diodes having a first electrode that contains two or more projections extending upwardly from a base, having at least one layer over the first electrode, and having a second electrode over the at least one layer.

RELATED PATENT DATA

This patent resulted from a continuation of U.S. patent application Ser.No. 12/141,265, which was filed Jun. 18, 2008, and which is herebyincorporated herein by reference.

TECHNICAL FIELD

Diodes, and methods of forming diodes.

BACKGROUND

Select devices are utilized in integrated circuitry for selectivelyaccessing components of the circuitry. Numerous device types may beutilized for select devices of integrated circuitry, with example devicetypes being diodes and transistors.

A continuing goal of integrated circuit fabrication is to increaseintegration density, and accordingly to decrease the footprint ofindividual devices by scaling the devices into it increasingly smallerdimensions. Select devices may be particularly difficult to scale inthat device performance may be reduced by decreasing the dimensions ofthe devices.

For instance, a parameter of diode performance that may be important inthe overall function of the diode is current flow through the diode. Aproblem that may occur when a diode is scaled into increasingly smallerdimensions is that the current flow through the diode may become toosmall relative to the intended operation of the diode.

It would be desirable to develop new diodes, and new methods of formingdiodes, which enable desired current flow to be maintained through thediodes as the diodes are scaled to a smaller footprint.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic, cross-sectional view of a portion of aconstruction illustrating an embodiment.

FIG. 2 is a graphical illustration of current versus voltage for adiode.

FIG. 3 shows three band-gap diagrams illustrating three different biasconditions of a diode in accordance with an embodiment.

FIG. 4 is a diagrammatic, cross-sectional view of a portion of aconstruction illustrating an embodiment.

FIG. 5 is a diagrammatic, cross-sectional view of a portion of aconstruction illustrating an embodiment.

FIG. 6 is a diagrammatic, cross-sectional view of a portion of aconstruction illustrating an embodiment.

FIGS. 7-10 are diagrammatic, cross-sectional views of a portion of aconstruction at various processing stages of an embodiment.

FIGS. 11-13 are diagrammatic, cross-sectional views of a portion of aconstruction at various processing stages of an embodiment.

FIGS. 14-17 are diagrammatic, cross-sectional views of a portion of aconstruction at various processing stages of an embodiment.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Some types of diodes comprise one or more materials sandwiched between apair of conductive electrodes. For instance, metal-insulator-metal (MIM)diodes may have one or more insulator materials sandwiched between apair of conductive electrodes. As another example, some types ofSchottky diodes may have one or more semiconductor materials sandwichedbetween a pair of conductive electrodes.

Conventional diode constructions will have the material that issandwiched between the conductive electrodes formed as a thin plane. Insome embodiments, it is recognized that if the diode constructions arefabricated to have an undulating topography between the two conductiveelectrodes, enhanced current flow may be obtained relative to diodeconstructions having a planar topography between the two conductiveelectrodes.

An example embodiment diode 12 is described with reference to FIG. 1 asa portion of a construction 10. The construction 10 may be supported bya semiconductor wafer, and accordingly may be a semiconductorconstruction.

The diode 12 comprises a lower electrode 14, an upper electrode 16, andan intermediate diode structure 18 sandwiched between the lowerelectrode and the upper electrode.

The lower electrode 14 comprises a base 20 and a pair of projections (orpedestals) 22 and 24 extending upwardly from the base. The basecomprises a base material 21, and the pedestals comprise conductivematerial 23. The materials 21 and 23 may be the same composition as oneanother in some embodiments, and in other embodiments materials 21 and23 may be compositionally different from one another.

The upper electrode 16 comprises a conductive material 17. Suchconductive material may be the same as one or both of materials 21 and23 of the lower electrode, or may be compositionally different from atleast one of the materials 21 and 23.

Conductive materials 21, 23 and 17 may comprise any suitable compositionor combination of compositions, and may, for example, comprise, consistessentially of, or consist of one or more of various metals (forinstance, tantalum, platinum, tungsten, aluminum, copper, gold, nickel,titanium, molybdenum, etc.), metal-containing compositions (forinstance, metal nitride, metal silicide such as tungsten silicide ortitanium silicide, etc.), and conductively-doped semiconductor materials(for instance, conductively-doped silicon, etc.).

Intermediate diode structure 18 may comprise any suitable composition orcombination of compositions, and may be a single homogeneous layer (asshown), or in other embodiments may comprise two or more distinctlayers. If diode 12 is a MIM, intermediate diode structure 18 maycomprise one or more electrically insulative compositions. For instance,intermediate diode structure 18 may comprise, consist essentially of, orconsist of one or more compositions selected from the group consistingof aluminum nitride, aluminum oxide, hafnium oxide, magnesium oxide,niobium oxide, silicon nitride, silicon oxide, tantalum oxide, titaniumoxide, yttrium oxide, and zirconium oxide. The oxides and nitrides arereferred to in tennis of the principle components, rather than in termsof specific stoichiometries. Accordingly, the oxide of silicon isreferred to as silicon oxide, which encompasses the stoichiometry ofsilicon dioxide.

If diode 12 utilizes Schottky diode characteristics, intermediate diodestructure 18 may comprise, consist essentially of, or consist of one ormore semiconductor materials (for instance, silicon); and the upper andlower electrodes may comprise, consist essentially of, or consist of oneor more metals and/or metal-containing compositions.

The pedestals 22 and 24 may be considered to comprise top surfaces 31and 33, respectively; and to comprise sidewall surfaces 35 and 37,respectively. The base 20 comprises an upper surface 39, and thesidewall surfaces of the pedestals extend from the upper surface 39 ofthe base to the uppermost surfaces 31 and 33 of the pedestals.

The surfaces 31, 33, 35, 37 and 39 together form an undulatingtopography of the first electrode 14. Such undulating topography hashighest surfaces corresponding to surfaces 31 and 33, and has a lowestsurface corresponding to surface 39. The highest surface is above thelowest surface by a distance “Q”. Such distance may be, for example, atleast about 50 nanometers; in some embodiments may be from about 50nanometers to about 500 nanometers; in some embodiments may be fromabout 200 nanometers to about 500 nanometers; and in some embodimentsmay be from about 50 nanometers to about one micron.

As discussed above, intermediate diode structure 18 may comprise one ormore layers. A total thickness of intermediate diode structure 18 may beless than or equal to about ten percent of the distance “Q”. In someembodiments, a thickness of intermediate diode structure 18 may be fromabout one nanometer to about four nanometers.

The pedestal 22 has a width “W”. Such width may be less than or equal toabout 50 nanometers in some embodiments.

An electrically insulative material 27 is over base 20, and the upperelectrode 16 is at least partially supported by such insulativematerial. The insulative material 27 may comprise any suitablecomposition or combination of compositions, and may, for example,comprise one or more of silicon nitride, silicon dioxide, andborophosphosilicate glass.

The electrodes 14 and 16, together with intermediate diode structure 18,form a diode. In other words, the first electrode 14, second electrode16, and intermediate diode structure 18 together form a structure thatconducts current between the first and second electrodes when voltage ofone polarity is applied to the structure, and that inhibits current flowbetween the first and second electrodes when voltage of an oppositepolarity is applied to the structure.

FIG. 2 shows a graph 2 that diagrammatically illustrates an exampleembodiment dependence of current flow on voltage for a diode structureof the type shown in FIG. 1. Specifically, positive voltage may beconsidered to be one polarity, and negative voltage may be considered tobe an opposite polarity. When positive voltage is applied there is highcurrent flow through the structure, and when negative voltage is appliedthere is relatively little current flow through the structure. A coupleof example datapoints “x” and “−x” are shown on the voltage scale.Although the embodiment of FIG. 2 shows increased current flow whenpositive voltage is applied and impedance when negative voltage isapplied, in other embodiments the increased current flow may occur whennegative voltage is applied and the impedance may occur when positivevoltage is applied.

As discussed above, intermediate diode structure 18 may comprisemultiple layers. Such layers may be band-gap engineered to createdesired diode properties. FIG. 3 shows an example embodiment in whichintermediate diode structure 18 comprises three layers 3, 5 and 7 whichare engineered to create desired diode properties. Specifically, FIG. 3shows band gap diagrams of diode 12 in an unbiased condition (diagram40), a forward biased condition (diagram 42) and a reverse biasedcondition (diagram 44). Diagrams 40 and 44 show that in an unbiasedcondition, and in a reverse biased condition, bands from dielectricmaterials 3, 5 and 7 preclude migration of carriers between conductivematerials 23 and 17. In contrast, diagram 42 shows that tunneling mayoccur in a forward biased condition so that carriers (specificallyelectrons in the shown embodiment) may tunnel from conductive material23 to conductive material 17 via quantum wells 43. The flow of theelectrons is diagrammatically illustrated with a dashed arrow 45 in FIG.3.

The band structures of FIG. 3 may be considered to be band-gapengineered structures. Heterostructures may be formed by molecular beamepitaxy (MBE) growth of III/V materials. In dielectric materials, a bandgap may be engineered through thermal treatments (such as thermaltreatment of aluminum oxides), as is known for nonvolatile memory cells(such as “crested barrier” cells and VARIOT flash cells). The band-gapengineered structures may exploit characteristics of band-edgediscontinuities in carrier transport in the semiconductor, and/or mayexploit characteristics of band-edge discontinuities in charge storageof the dielectric.

The diode 12 of FIG. 1 is one example embodiment diode. Other exampleembodiment diodes are shown in FIGS. 4-6.

FIG. 4 shows a portion of a construction 50 comprising a diode 52.Construction 50 may be a semiconductor construction. The diode 52includes a lower electrode 54 comprising a base 60 and a single pedestal62 extending upwardly from the base. The diode also includes an upperelectrode 56 and the intermediate diode structure 18 between the upperand lower electrodes. The base 60 and pedestal 62 of the lower electrodemay comprise any of the compositions discussed above with reference toFIG. 1 for the base 20 and pedestals 22 and 24; and the upper electrode56 of FIG. 4 may comprise any of the compositions discussed above withreference to FIG. 1 for the upper electrode 16. Portions of the upperelectrode are supported by the insulative material 27. The pedestal 62may have a width suitable for fabrication utilizing conventionalpatterning.

FIG. 5 shows a portion of a construction 70 comprising a diode 72. Theconstruction 70 may be a semiconductor construction. The diode 72includes a lower electrode 74 comprising a base 80 and a plurality ofpedestals 82, 84 and 86 extending upwardly from the base. The diode alsoincludes an upper electrode 76, and comprises the intermediate diodestructure 18 between the upper and lower electrodes. The base 80 andpedestals 82, 84 and 86 of the lower electrode may comprise any of thecompositions discussed above with reference to FIG. 1 for the base 20and pedestals 22 and 24; and the upper electrode 76 of FIG. 5 maycomprise any of the compositions discussed above with reference to FIG.1 for the upper electrode 16. Portions of the upper electrode aresupported by the insulative material 27. The pedestals 82, 84 and 86 mayhave widths suitable for fabrication utilizing conventional patterning;and at least one of the pedestals may have a different width than atleast one other of the pedestals (as shown), or in other embodiments allof the pedestals may have the same widths as one another.

FIG. 6 shows a portion of a construction 100 comprising a diode 102. Theconstruction 100 may be a semiconductor construction. The diode 102includes a lower electrode 104 comprising a base 110 and a plurality ofpedestals 112, 114, 116, 118, 120 and 122 extending upwardly from thebase. The diode also includes an upper electrode 106, and comprises theintermediate diode structure 18 between the upper and lower electrodes.The base 110 and pedestals 112, 114, 116, 118, 120 and 122 of the lowerelectrode may comprise any of the compositions discussed above withreference to FIG. 1 for the base 20 and pedestals 22 and 24; and theupper electrode 106 of FIG. 6 may comprise any of the compositionsdiscussed above with reference to FIG. 1 for the upper electrode 16.Portions of the upper electrode are supported by the insulative material27. The pedestals 112, 114, 116, 118, 120 and 122 may be too narrow forfabrication utilizing conventional patterning, and instead may be formedby seeding followed by growth of columns over the seeds, as discussedbelow with reference to FIGS. 14-17.

The diodes described above may be formed by any suitable methods. Anexample method for forming a diode analogous to that of FIG. 1 isdescribed with reference to FIGS. 7-10.

Referring to FIG. 7, construction 10 is shown at a processing stage inwhich insulative material 27 is formed over base 20, and is patterned tohave an opening 120 extending therethrough. The patterning of material27 may comprise photolithographic processing. Specifically, material 27may be formed as a uniform expanse across base 20, aphotolithographically-patterned photoresist mask (not shown) may beformed over material 27, a pattern may be transferred from thephotoresist mask to material 27 with one or more suitable etches, andthe photoresist mask may then be removed to leave the shown constructionof FIG. 7.

Referring to FIG. 8, electrically conductive material 23 is formedacross material 27 and within opening 120. The conductive materialpartially fills the opening to narrow the opening. Spacer material 122is formed within the narrowed opening as a pair of spacers 123 along thesidewalls of the narrowed opening. The spacers may be fabricated byinitially forming a continuous layer of spacer material 122 acrossmaterial 27 and within opening 120, and then subjecting the spacermaterial to an anisotropic etch to remove most of the spacer materialwhile leaving the shown spacers.

Referring to FIG. 9, construction 10 is illustrated after utilization ofthe spacers 123 (FIG. 8) as a mask to pattern the material 23, and aftersubsequent removal of the spacers.

Referring to FIG. 10, intermediate diode structure 18 is formed bydeposition of one or more layers over materials 23 and 27, and withinopening 120; and subsequently the second electrode 16 is formed over theintermediate diode structure 18. The one or more layers of intermediatediode structure 18 may be formed by any suitable method. The layers ofintermediate diode structure 18 may be formed to be very conformalacross the underlying materials if they are formed by atomic layerdeposition (ALD).

The construction of FIG. 10 comprises a diode 124 similar to the diode12 of FIG. 1. Like diode 12 of FIG. 1, the diode 124 comprises pedestals22 and 24 of material 23 extending upwardly from base 20.

In some embodiments (not shown), the material 23 of the pedestals may bepatterned with a mask other than the spacers of FIG. 8, so that some ofthe material 23 is left to extend across the base in a gap 126 betweenthe pedestals 22 and 24. In some embodiments, spacers 123 (FIG. 8) maybe omitted, and the liner 23 may be anisotropically etched to form theprojections 22 and 24.

FIGS. 11-13 illustrate an example method for forming the diode 52 ofFIG. 4.

Referring to FIG. 11, construction 50 is shown at a processing stage inwhich insulative material 27 is formed over base 60, and patterned tohave an opening 130 extending therethrough. The patterning of material27 may comprise photolithographic processing, as discussed aboverelative to FIG. 7. Spacer material 131 is formed within opening 130,and patterned into a pair of spacers 135. The spacers may be fabricatedby initially forming a continuous layer of spacer material 131 acrossmaterial 27 and within opening 130, and then subjecting the spacermaterial to an anisotropic etch to remove most of the spacer materialwhile leaving the shown spacers. A narrowed opening 133 extends betweenthe spacers 135.

Referring to FIG. 12, construction 50 is shown after formingelectrically conductive material 132 within the narrowed opening 133(FIG. 11) between the spacers 135 (FIG. 11), and after subsequentremoval of the spacers. Openings 136 and 138 are in locations where thespacers were removed from. The construction of FIG. 12 may be consideredto have a pedestal 62 of material 132 projecting upwardly from base 60.

Referring to FIG. 13, intermediate diode structure 18 is formed bydeposition of one or more layers over materials 60, 132 and 27; andsubsequently the second electrode 56 is formed over intermediate diodestructure 18 to complete formation of diode 52. The one or more layersof intermediate diode structure 18 may be formed by any suitable method,including, for example, ALD.

FIGS. 14-17 illustrate an example method for forming a diode analogousto the diode 102 of FIG. 6.

Referring to FIG. 14, construction 100 is shown at a processing stage inwhich insulative material 27 is formed over base 110, and is patternedto have an opening 150 extending therethrough. A layer of material 152is formed across insulative material 27 and within opening 150. In someembodiments, material 152 is a sacrificial material, and accordingly thematerial may comprise any composition selectively removable relative toother compositions of construction 100. For instance, in someembodiments material 152 may comprise, consist essentially of, orconsist of silicon dioxide, silicon nitride or silicon oxynitride.

Referring to FIG. 15, material 152 is anisotropically etched to form thematerial into sidewall spacers 154. The sidewall spacers 154 are alongsidewalls of material 27 at the periphery of opening 150, and narrow theopening. The opening is shown to have a first width 153, and theinsulative material is shown to narrow such width to a second width 155.In some embodiments, the first width 153 may be from about 200nanometers to about two microns, and the sidewall spacers 154 may havewidths of from about 50 angstroms to about 100 angstroms, so that thesecond width 155 is at least about 90 percent of the first width.

Referring to FIG. 16, seed material 156 is dispersed along a bottom ofopening 150. In the shown embodiment, an upper surface of conductivebase 110 is exposed along the bottom of opening 150, and the seedmaterial is dispersed directly on such upper surface of the base. Thesidewall spacers 152 preclude the seed material from being directlyagainst the sides of insulative material 27.

The seed material may be electrically conductive, and may, for example,be metal-containing nanocrystals (such as, for example, nanocrystalscomprising one or more of platinum, nickel, gold, silver, copper,palladium, tungsten, titanium, ruthenium, etc.). The term “nanocrystals”is used herein to refer to crystalline material (either polycrystallineor monocrystalline) having a maximum cross-sectional dimension of lessthan or equal to about 10 nanometers. The seed material may consist ofnanocrystals (in other words, may consist of nanocrystalline seeds), ormay comprise nanocrystals in combination with other seed material thatis larger than nanocrystals.

Referring to FIG. 17, spacers 154 are removed, and electricallyconductive pedestals 112, 114, 116, 118, 120 and 122 are formed overseeds 156 (FIG. 16) by growing conductive material 158 over the seedmaterial. The conductive material may, for example, comprise, consistessentially of, or consist of nanorods of conductively-doped silicon,carbon and/or other appropriately electrically conductive materialsformed using chemical vapor deposition (CVD), plasma CVD, molecular-beamepitaxy (MBE) or any other suitable deposition techniques.

Pedestals 112, 114, 116, 118, 120 and 122 may be considered to be spacedfrom one another by valleys, and an undulating topography of a surfaceof the lower electrode may be considered to extend over the pedestalsand down into the valleys.

Pedestals 112, 114, 116, 118, 120 and 122 of FIG. 17 are similar tothose of FIG. 6, except that some of the pedestals of FIG. 17 are atdifferent heights relative to others, whereas the pedestals of FIG. 6are all of the same height. FIGS. 6 and 17 thus illustrate similar butslightly different embodiments.

Intermediate diode structure 18 is formed by deposition of one or morelayers over and between pedestals 112, 114, 116, 118, 120 and 122; andsubsequently the second electrode 106 is formed over intermediate diodestructure 18 to complete formation of diode 102. The one or more layersof intermediate diode structure 18 may be formed by any suitable method,including, for example, ALD.

The various methods described with reference to FIGS. 7-17 show singlediodes being formed. The single diodes may be representative a largeplurality of diodes that are simultaneously formed as part of anintegrated circuit fabrication process. The diodes may be part of, forexample, a memory array or a logic circuit. Thus, the single openings120, 130 and 150 of FIGS. 7, 11 and 14, respectively, may berepresentative of large pluralities of openings that are simultaneouslysubjected to identical processing.

In some embodiments, two or more of the above-discussed embodiments maybe combined. For instance, the processing of FIGS. 7-9 may be utilizedto form a pair of pedestals of a lower diode electrode, and theprocessing of FIGS. 11-12 and/or the processing of FIGS. 14-17 mayutilized to form additional pedestals of the lower electrode.

The diodes formed in accordance with various embodiments may be utilizedfor selectively accessing various integrated circuit components, such asmemory cells, logic devices, etc. Integrated circuitry comprising suchdiodes may be utilized in a broad range of electronic systems, such as,for example, clocks, televisions, cell phones, personal computers,automobiles, industrial control systems, aircraft, etc.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

1. A method of forming a diode, comprising: forming an electricallyconductive lining within an opening, the opening being bounded byelectrically insulative sidewalls and by an electrically conductivebottom, the lining extending along the sidewalls and bottom to narrowthe opening but not completely fill the opening; patterning the lininginto one or more pedestals; said pedestals having top surfaces, andhaving sidewall surfaces extending downwardly from the top surfaces;depositing one or more layers across the top surfaces and the sidewallsurfaces of the one or more pedestals; forming an electrode over saidone or more layers; and wherein the one or more pedestals, one or morelayers, and electrode together are the diode.
 2. The method of claim 1wherein the one or more layers are at least two layers.
 3. The method ofclaim 1 wherein the one or more layers are only one layer.
 4. A methodof forming a diode, comprising: forming an electrically insulativematerial over an electrically conductive base, the electricallyinsulative material having a thickness over the base; forming an openingextending through the electrically insulative material to an uppersurface of the electrically conductive base; dispersing seed materialalong the upper surface of the electrically conductive base at a bottomof the opening; growing pedestals from the dispersed seed material, thepedestals being spaced from one another by valleys, an undulatingtopography extending across the pedestals and valleys, the pedestals andbase together being a first electrode; the pedestals having heights nogreater than the thickness of the electrically insulative material;forming one or more layers across the undulating topography; forming asecond electrode over said one or more layers; and wherein the firstelectrode, one or more layers, and second electrode together are thediode.
 5. The method of claim 4 wherein the dispersed seed materialconsists of nanocrystalline seeds.
 6. The method of claim 4 furthercomprising forming at least one sidewall spacer along a sidewall of theopening prior to dispersing the seed material; and removing the at leastone sidewall spacer after dispersing the seed material.
 7. The method ofclaim 4 wherein the forming of the one or more layers comprises atomiclayer deposition.
 8. A semiconductor construction, comprising: a firstelectrode supported by a semiconductor wafer, the first electrode havingan undulating topography, the undulating topography comprising a lowestsurface and a highest surface; the highest surface being above thelowest surface by a distance; the electrode being within an opening inan electrically insulative material; the electrically insulativematerial having a thickness over the semiconductor wafer and thedistance between the highest and lowest surfaces being no greater thanthe thickness of the electrically insulative material; one or morelayers across the undulating topography, the one or more layers togetherhaving a thickness that is less than or equal to about 10% of thedistance; a second electrode over said one or more layers; wherein thefirst electrode, one or more layers, and second electrode together aretogether a diode; and wherein the diode is a Schottky diode.
 9. Thesemiconductor construction of claim 8 wherein the distance is at leastabout 50 nanometers.